1. Field of the Invention
The present invention relates generally to imaging of three-dimensional (xe2x80x9c3Dxe2x80x9d) volume data sets. More particularly, the present invention relates to fast visualization and analysis of very large 3D volume data sets using 3D computer graphics.
2. Related Art
Many fields of endeavor require the analysis and imaging of three-dimensional (xe2x80x9c3Dxe2x80x9d) volume data sets. For example, in the medical field, a CAT (computerized axial tomography) scanner or a magnetic resonance imaging (MRI) device is used to produce a xe2x80x9cpicturexe2x80x9d or diagnostic image of some part of a patient""s body. The scanner or MRI device generates a 3D volume data set that needs to be imaged or displayed so that medical personnel can analyze the image and form a diagnosis.
Three-dimensional volume data sets are also used in various fields of endeavor relating to the earth sciences. Seismic sounding is one method for exploring the subsurface geology of the earth. An underground explosion or earthquake excites seismic waves, similar to low frequency sound waves, that travel below the surface of earth and are detected by seismographs. The seismographs record the time of arrival of the seismic waves, both direct and reflecte waves. Knowing the time and place of the explosion or earthquake, the time of travel of the waves through the interior can be calculated and used to measure the velocity of the waves in t interior. A similar technique can be used for offshore oil and gas exploration. In offshore exploration, a ship tows a sound source and underwater hydrophones. Low frequency (e.g., 50 Hz) sound waves are generated by, for example, a pneumatic device that works like a bal burst. The sounds bounce off rock layers below the sea floor and are picked up by the hydrophones. In this manner, subsurface sedimentary structures that trap oil, such as faults, folds, and domes, are xe2x80x9cmappedxe2x80x9d by the reflected waves. The data is processed to produce volume data sets that include a reflection or seismic amplitude datavalue at specified (x, y, z) locations within a geographic space.
A 3D volume data set is made up of xe2x80x9cvoxelsxe2x80x9d or volume elements. Each voxel has a numeric value for some measured or calculated property, e.g., seismic amplitude, of the volume at that location. One conventional approach to generating an image of a 3D volume data set is to cross-section the 3D volume data set into a plurality of two-dimensional (xe2x80x9c2Dxe2x80x9d) cross-sections or slices. The image of the 3D volume data set is then built as a composite of the 2D slices. For example, the image of the 3D volume data set is generated by stacking the 2D slices in order, back-to-front, and then composited into a complete image. The user sees the image being built layer by layer as the composite grows. Although the user can see the internal organization or structure of the volume as the composite image grows, the traditional slice and composite technique is typically slow, particularly when very large 3D volume data sets are being used. Additionally, the slice and composite technique clutters the user""s field of view with extraneous information, and interferes with the user""s ability to accurately visualize and interpret features inherent in the 3D volume data set.
Computer software has been developed specifically for imaging 3D seismic data sets for the oil and gas industry. Examples of such conventional computer programs include VoxelGeo, available from Paradigm Geophysical, Houston, Tex., SeisWorks and EarthCube, available from Landmark Graphics Corporation, and IESX, available from GeoQuest. Such conventional computer programs have numerous deficiencies that preclude a user from quickly and accurately visualizing and interpreting features inherent in a 3D seismic data set. Conventional computer programs for visualizing and interpreting 3D seismic data operate on the full 3D volume of seismic data. Consequently, every time a change is made, such as a change to the transparency or opacity settings, the full 3D volume of seismic data must be processed, and the image re-drawn. Even when such programs are run on highly efficient graphics supercomputers, the delay or lag in re-drawing the image is perceptible to the user. For a 3D volume containing 500 megabytes of seismic data, it can take on the order of 30-45 seconds for conventional programs to re-draw the complete image (frame rate of 0.03 to 0.02 frames per second, respectively). During the 30-45 second delay time, the mind of the user loses focus on the feature of interest, making it difficult to completely and properly analyze the seismic data.
Some conventional 3D seismic interpretation programs provide the capability to visualize and interpret a piece of the full 3D volume of seismic data. The user identifies the coordinates of the selected piece via a menu command. An image of the selected piece is drawn. The selected piece can then be rotated, if desired, at that location. However, to look at a different piece of the full 3D volume of seismic data, such as to follow a geologic feature that has been tentatively identified, the image must be interrupted, a new location or coordinates for the different piece is entered, and a new image is drawn containing the different piece. The interruption in the displayed image makes it difficult for the user to visualize any continuity between the two pieces of the full 3D volume of seismic data that have been imaged. This impedes the user""s ability to interpret and identify the geologic features that are inherent in the full 3D volume of seismic data. Additionally, even though only a piece of the full 3D volume of seismic data is being visibly displayed, conventional 3D seismic interpretation programs continue processing the full 3D volume of seismic data to draw the image, thereby slowing the display of the image to the user.
Conventional 3D seismic interpretation programs provide the capability to xe2x80x9cauto pickxe2x80x9d and identify points that satisfy a voxel selection algorithm. However, these programs typically iterate through the full 3D volume of seismic data to identify the points that satisfy the voxel selection algorithm. This is time consuming even on a high speed graphics supercomputer. Additionally, conventional 3D seismic interpretation programs do not provide the capability to directly delete from the collection of picked voxels. The only way to xe2x80x9celiminatexe2x80x9d points from the collection of picked voxels using conventional 3D seismic interpretation programs is to repeatedly adjust the selection criteria for the voxel selection algorithm until the points to be eliminated fall outside of the selection criteria for the displayed points that satisfy the voxel selection algorithm. Each time the selection criteria is adjusted, the image must be interrupted. This iterative process is time consuming, and interferes with the visualization process of the user.
Thus, there is a need in the art for a system and method for imaging 3D volume data sets that overcomes the deficiencies detailed above. Particularly, there is a need for a system and method that re-draws images of large 3D volume data sets in response to user input at a rate sufficiently fast that the user perceives an instantaneous or real-time change in the image, without perceptible delay or lag. There is a need for a system and method that allows a user to interactively change the displayed image in a continuous manner, without interruption or perceptible delay or lag. Such a system and method would allow a user to more quickly and accurately interpret and identify features inherent in 3D volume data sets.
The present invention is directed to a system and method for analyzing and imaging 3D volume data sets using a 3D sampling probe. In one aspect of the invention, a program storage device is provided. The program storage device is readable by a machine, and tangibly embodies a program of instructions executable by the machine to perform method steps of imaging a 3D volume defined by a data set of voxels, each voxel expressed in the form of (x, y, z, datavalue).
The method steps comprise the following steps:
(a) creating one or more three-dimensional (3D) sampling probe(s), wherein each 3D sampling probe is a sub-volume of the 3D volume;
(b) drawing an image of the 3D sampling probe(s) for display to a user, the image comprising an intersection of the 3D sampling probe(s) and the 3D volume; and
(c) repeating drawing step (b) responsive to input from the user to move a location of the 3D sampling probe(s) within the 3D volume so that as the 3D sampling probe(s) moves through the 3D volume, the image of the 3D sampling probe(s) is re-drawn sufficiently fast to be perceived as real-time by the user, thereby enabling the user to visualize a feature defined by the data values.
In another aspect of the invention, the method steps further comprise the following step:
(d) repeating drawing step (b) responsive to input from the user to re-shape the 3D sampling probe(s) so that as the 3D sampling probe(s) is changed in shape, the image of the 3D sampling probe(s) is re-drawn sufficiently fast to be perceived as real-time by the user.
In a further aspect of the invention, the method steps further comprise identifying a seed point that is within a data set of voxels that defines an auto picking 3D sampling probe, and defining a selection criteria based on datavalues. Points connected to the seed point that have datavalues satisfying the selection criteria are identified as selected points. As the auto picking 3D sampling probe moves through the 3D volume, the image of the auto picking 3D sampling probe contains selected points within the auto picking 3D sampling probe sub-volume, and the image is re-drawn sufficiently fast to be perceived as real-time by the user.
In yet a further aspect of the invention, the method steps further comprise defining an eraser 3D sampling probe, and defining a de-selection criteria based on datavalues. Points previously selected by an auto picking operation that satisfy the de-selection criteria are identified as candidates for de-selection. As the eraser 3D sampling probe moves through the 3D volume, the de-selected points are deleted from the image, and the image is re-drawn sufficiently fast to be perceived as real-time by the user.
In still a further aspect of the present invention, a method is provided for imaging a three-dimensional (3D) data volume representing a geographic space for visualization and interpretation of physical parameters of the geographic space by a user, wherein the 3D data volume is defined by a data set of voxels, each voxel expressed in the form of (x, y, z, datavalue), the method comprising:
(a) creating one or more three-dimensional (3D) sampling probe(s), wherein each 3D sampling probe is a sub-volume of the 3D data volume;
(b) drawing an image of the 3D sampling probe(s) for display to a user, the image comprising an intersection of the 3D sampling probe(s) and the 3D data volume; and
(c) repeating drawing step (b) responsive to input from the user to move a location of the 3D sampling probe(s) within the 3D data volume so that as the 3D sampling probe(s) moves through the 3D data volume, the image of the 3D sampling probe(s) is re-drawn sufficiently fast to be perceived as real-time by the user, thereby enabling the user to visualize and interpret physical parameters in the geographic space.
In still a further aspect of the invention, a computer program product is provided that comprises a computer useable medium having computer program logic recorded thereon for enabling a processor in a computer system to image a three-dimensional (3D) seismic data volume for visualization and interpretation of geologic features by a user, the 3D seismic data volume being defined by a data set of voxels, each voxel expressed in the form of (x, y, z, seismic amplitude). The computer program product comprises: probe creating means for enabling the processor to create one or more three-dimensional (3D) sampling probe(s), each 3D sampling probe being a sub-volume of the 3D seismic data volume; image drawing means for enabling the processor to draw an image of the 3D sampling probe(s) for display to a user, the image comprising an intersection of the 3D sampling probe(s) and the 3D seismic data volume; and drawing repeating means for enabling the processor to repeatedly draw responsive to input from the user to move a location of the 3D sampling probe(s) within the 3D seismic data volume so that as the 3D sampling probe(s) moves through the 3D seismic data volume, the image of the 3D sampling probe(s) is re-drawn sufficiently fast to be perceived as real-time by the user, thereby enabling the user to visualize and interpret geologic features.
In yet a further aspect of the invention, a system is provided for imaging a three-dimensional (3D) seismic data volume for visualization and interpretation of geologic features by a user, the 3D seismic data volume being defined by a data set of voxels, each voxel expressed in the form of (x, y, z, seismic amplitude). The system comprises: means for creating one or more three-dimensional (3D) sampling probe(s), each 3D sampling probe being a sub-volume of the 3D seismic data volume; image drawing means for drawing an image of the 3D sampling probe(s) for display to a user, the image comprising an intersection of the 3D sampling probe(s) and the 3D seismic data volume; and drawing repeating means for repeatedly drawing the image of the 3D sampling probe(s) responsive to input from the user to move a location of the 3D sampling probe(s) within the 3D seismic data volume so that as the 3D sampling probe(s) moves through the 3D seismic data volume, the image of the 3D sampling probe(s) is re-drawn sufficiently fast to be perceived as real-time by the user, thereby enabling the user to visualize and interpret geologic features.
It is a feature of the present invention that, as a user interactively moves a 3D sampling probe through a 3D volume data set, the image on the surfaces of the 3D sampling probe is re-drawn xe2x80x9con the flyxe2x80x9d so that the user perceives the image changing in real-time with movement of the 3D sampling probe. Similarly, as a user interactively moves a 3D sampling probe through a 3D volume data set, the 3D sampling probe is volume rendered with varying degrees of transparency xe2x80x9con the flyxe2x80x9d so that the user perceives the image changing in real-time with movement of the 3D sampling probe.
It is a further feature of the present invention that a user can interactively change the shape or size of a 3D sampling probe so that the image on the surfaces of the 3D sampling probe is re-drawn xe2x80x9con the flyxe2x80x9d so that the user perceives the image changing in real-time with the change in shape or size of the 3D sampling probe. Similarly, a user can interactively change the shape or size of a 3D sampling probe so that the 3D sampling probe is volume rendered with varying degrees of transparency xe2x80x9con the flyxe2x80x9d so that the user perceives the image changing in real-time with the change in shape or size of the 3D sampling probe.
It is yet a further feature of the present invention that a user can interactively rotate a 3D sampling probe so that the image on the surfaces of the 3D sampling probe is re-drawn xe2x80x9con the flyxe2x80x9d so that the user perceives the image changing in real-time with the rotation of the 3D sampling probe. Similarly, a user can interactively rotate a 3D sampling probe so that the 3D sampling probe is volume rendered with varying degrees of transparency xe2x80x9con the flyxe2x80x9d so that the user perceives the image changing in real-time with the rotation of the 3D sampling probe.
It is yet a further feature of the present invention that an eraser 3D sampling probe can be created and manipulated by the user to directly delete from an image selected points that fall within a certain datavalue range.
It is an advantage of the present invention that a user can manipulate a 3D sampling probe to interactively traverse a 3D volume data set to continuously follow and image a feature.
It is a further advantage of the present invention that a user can interactively change the displayed image in a continuous manner, without interruption or perceptible delay or lag. This allows a user to more quickly and accurately interpret and identify features inherent in 3D volume data sets.
It is yet a further advantage of the present invention that the 3D sampling probes can be interactively re-shaped by the user to match the shape of geologic features, thereby enabling the user to better visualize and define the extent of geologic features.
A still further advantage of the present invention is that it can be used to visualize and interpret large volumes of 3D seismic data. The present invention can be used to quickly and accurately identify drilling sites. The present invention can advantageously be used to sharply reduce 3D seismic project cycle times, to boost production from existing wells, and to locate additional reserves.